package java6681.lesson10;

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double max = sc.nextDouble();
        double min = sc.nextDouble();
        double x1 = sc.nextDouble();
        double x2 = sc.nextDouble();
        int[] num = getAnswer(max, min, x1, x2);
        System.out.println(Arrays.toString(num));
    }

    public static int[] getAnswer(double max, double min, double x1, double x2) {
        int k = 0;
        int a = (int) Math.ceil(max);
        int b = (int) Math.ceil(min);

        if (max > 0 && min > 0 && max > min) {
            return null;
        }

        if ((b - a + 1) < 0) {
            return null;
        }
        int[] num = new int[b - a + 1];
        for (int i = a; i < b; i++) {
            int abs = Math.abs(i);
            if (abs > x1 || abs < x2) {
                num[k++] = i;
            }
        }
        if (x1 < 0 || x2 < 0 || x1 < x2) {
            return null;
        }
        return Arrays.copyOfRange(num, 0, k);
    }
}